Speed change control method and device of automatic transmission for vehicle

ABSTRACT

While running of an engine used to be unstable in warming-up, the output of the engine is large and the running of the engine is maintained stably in high vehicle speed even if the engine is in the warming-up. According to the present invention, an automatic transmission is allowed to be run in the high speed stage in the high vehicle speed even during the warming-up.

This is a continuation of application Ser. No. 753,552, filed July 10,1985, which was abandoned upon the filing hereof, which in turn was acontinuation of Ser. No. 338,051 filed Jan. 8, 1982, now U.S. Pat. No.4,572,029 issued Feb. 25, 1986.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a speed change control method and device of anautomatic transmission for a vehicle provided with an electronic controlfor controlling oil pressure supply to a hydraulic servo for a frictionengaging device according to electric signals.

2. Description of the Prior Art

In a prior automatic transmission to maintain the drivability, at a lowengine temperature, a speed change to a predetermined high speed stage(speed change stage producing reduction gear ratio lower than apredetermined value) is prohibited at the low temperature of the engineirrespective of vehicle speed. However, when the vehicle proceedsrapidly to high speed travelling after starting the engine, the outputof the engine is sufficiently large so that no obstacles against thedrivability are encountered in the travelling at the high speed stage.Namely, in the prior automatic transmission, the vehicle is driven atthe low speed stage even though in such a case disadvantages areproduced such as inefficiency of fuel comsumption and restraint innoxious exhaust gas component production.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a speed change controlmethod and device of an automatic transmission for a vehicle, whichimproves the efficiency of fuel consumption and purges noxious exhaustgas components at low engine temperatures during high speed travelling.

According to the speed change control method of the automatictransmission for the vehicle, according to the present invention toachieve this object, when the engine temperature is lower than apredetermined value and the vehicle speed is higher than a predeterminedvalue, a speed change stage is allowed to produce a reduction gear ratiolower than the predetermined value and when the vehicle speed is lowerthan the predetermined value said speed change stage is prohibited frombeing operated.

Also, the speed change control device of the automatic transmission forthe vehicle according to the present invention is provided with a firstvoltage producing means for producing voltage related to the enginetemperature, a second voltage producing means for producing voltagerelated to vehicle speed, a first comparator for comparing the outputvoltage of the first voltage producing means with a first predeterminedvalue, a second comparator for comparing the output voltage of thesecond voltage producing means with a second predetermined value, an oilpressure supply controlling means for controlling oil pressure supply toa hydraulic servo for a friction engaging device upon receivingoperating signals when a speed change stage producing reduction gearratio lower than a predetermined value is carried out and a blockingmeans for blocking the input of the operating signal to the oil pressuresupply controlling means only when the engine temperature is lower thana predetermined value and the vehicle speed is lower than apredetermined value in response to the outputs of the first and secondcomparators.

As a result, even if the engine is still in low temperature withoutbeing sufficiently warmed up, the automatic transmission can be changedover to the high speed stage in the high speed travelling withsufficiently large output of the engine. Thus, running time at the highspeed stage is increased, efficiency of fuel consumption improved andpurge amount of noxious components restrained without impairing thedrivability in the warming-up.

In preferred embodiments of the present invention, the enginetemperature is detected from temperature of cooling water, lubricatingoil or cylinder head corresponding to the engine temperature. Also,preferably the automatic transmission is of an advance four speed typeand the fourth speed provides over-drive. The speed change stageprohibited when the engine temperature is lower than a predeterminedvalue and the vehicle speed is lower than a predetermined value providespreferably the fourth speed or the third speed and the fourth speed.Further in the embodiments of the present invention, a requirement forprohibiting the third speed is made different from that for prohibitingthe fourth speed, and set values of the cooling water temperature andvehicle speed for prohibiting the fourth speed are made larger thanthose for prohibiting the third speed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of the whole electronic controlengine according to the present invention;

FIG. 2 is a block diagram of an electronic control shown in FIG. 1;

FIGS. 3(a) and 3(b) are drawings exemplifying a hydraulic controlcircuit having hydraulic connection changed over by a solenoid;

FIG. 4 is a flow chart of an example of a program according to a methodof the present invention;

FIG. 5 is a schematic drawing of an embodiment of the device accordingto the present invention;

FIG. 6 is a graph showing the input-output characteristics of a F/Vconverter shown in FIG. 5; and

FIG. 7 is a graph showing the relationship between cooling watertemperature and the output voltage of a water temperature sensor shownin FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter will be described the embodiments of the present inventionwith reference to the drawings.

FIG. 1 is a schematic illustration of an electronic control fuelinjection engine according to the present invention. Air sucked throughan air cleaner 1 is sent to a combustion chamber 8 of an engine body 7through an intake path 12 including an air flow meter 2, throttle valve3, surge tank 4, intake port 5 and intake valve 6. The throttle valve 3is interlocked with an accelerator pedal 13 in a cab. The combustionchamber 8 is defined by a cylinder head 9, cylinder block 10 and piston11, and exhaust gas produced by the combustion of fuel mixture is purgedto the atmospheric air through an exhaust valve 15, exhaust port 16,exhaust manifold 17 and exhaust pipe 18. The upstream side of thethrottle valve 3 is connected to the surge tank 4 through a bypass path21, and a bypass flow controlling valve 22 controls the sectional areaof the flow in the bypass path 21 to maintain constant rotational speedof the engine in idling. An exhaust gas recirculation (EGR) path 23 forconducting exhaust gas to an intake system to restrain the production ofnitric oxide connects the exhaust manifold 17 to the surge tank 4, andan exhaust gas recirculation (EGR) controlling valve 24 of a on-offvalve type opens and closes the EGR path 23 in response to electricpulses. An intake temperature sensor 28 provided in the air flow meter 2detects intake temperature and a throttle position sensor 29 detects theopening of the throttle valve 3. A water temperature sensor 30 mountedon the cylinder block 10 detects cooling water temperature, i.e. enginetemperature, and air fuel ratio sensor 31 well known for an oxygenconcentration sensor is mounted on the aggregate portion of the exhaustmanifold 17 to detect the oxygen concentration in the aggregate portion.A crank angle sensor 32 detects the crank angle of crank shaft from therotation of a shaft 34 of a distributor 33 coupled to a crank shaft (notshown) of the engine body 7. A vehicle speed sensor 35 detects therotational speed of the output shaft of the automatic transmission 36.The outputs of these sensors 2, 28, 29, 30, 31, 32, 35 and voltage of anaccumulator 37 are sent to an electronic control 40. Fuel injectionvalves 41 are respectively provided near the respective intake ports 5corresponding to the respective cylinders, and a pump 42 sends fuel froma fuel tank 43 through a fuel path 44 to the fuel injection valve 41.The electronic control 40 calculates the fuel injection amount by theuse of the input signals from the respective sensors as parameters tosend electric pulses with pulse width corresponding to the calculatedfuel injection amount to the fuel injection valve 41. Also, theelectronic control 40 controls the bypass flow controlling valve 22, EGRcontrolling valve 24, solenoid 45 in a hydraulic control circuit of theautomatic transmission and an ignition unit 46. The secondary side of anignition coil in the ignition unit 46 is connected to the distributor33.

FIG. 2 is a block diagram of the interior of the electronic control. CPU(Central Processing Unit) 56, ROM (Read-Only Memory) 57, RAM (RandomAccess Memory) 58, 59, A/D (Analog/Digital) Converter 60 withmultiplexer and input/output interface 61 are connected to each otherthrough a bus 62. RAM 59 is connected to an auxiliary power source sothat a predetermined electric power is supplied to maintain memory whilean ignition switch is opened and the engine is stopped. Analog signalsfrom the air flow meter 2, intake temperature sensor 28, watertemperature sensor 30 and air fuel ratio sensor 31 are sent to the A/Dconverter. The outputs of the throttle position sensor 29, crank anglesensor 32 and vehicle speed sensor 35 are sent to the input/outputinterface 61 which sends the input signals to the bypass flowcontrolling valve 22, EGR controlling valve 24, solenoid 45 and ignitionunit 46.

FIG. 3 shows the solenoid 45 in the hydraulic control circuit. A speedchange valve 65 is provided with an input port 66 having line pressuresent from a manual valve (not shown) operated by a speed change lever inthe cab, an output port 70 connected to an oil chamber 69 in thehydraulic servo 68 for a brake band 67 as the friction engaging deviceof the automatic transmission 36, a spool 71 for controlling theconnection between the ports 66, 70 and a spring 72 for urging the spool71 towards solenoid 45. A rod 73 protrudes to displace the spool 71against the spring 72 when the solenoid 45 is energized (FIG. 3(a)) andthe input port 66 is disconnected from the output port 70. Thus, theline pressure is not supplied to the oil chamber 69 in the hydraulicservo 68 so that the brake band 67 is in the engaging condition due tothe line pressure in the other oil chamber 74 of the hydraulic servo 68.Also, when the solenoid 45 is deenergized (FIG. 3(b)), the rod 73 ispulled in by the solenoid 45, the spool 71 is moved towards the solenoid45 by the spring 72 to connect the input port 66 to the output port 70.Thus, the line pressure is supplied to the oil chamber 69 in thehydraulic servo 68 to release the brake band 67.

FIG. 4 is a flow chart of an example of program according to the presentinvention. The embodiment of the automatic transmission 36 is assumed tobe of an advance four speed type and the fourth speed assumed to provideover drive. In step 77 is judged by the input signals from the watertemperature sensor 30 whether or not the cooling water temperaturecorresponding to the engine temperature is lower than 60° C. and theprogram proceeds to step 78 if it is judged yes and terminates if no.Namely, if the cooling water temperature is higher than 60° C., thevehicle is run with the first to fourth speeds on relation to thevehicle speed and engine load. In step 78 is judged whether or not thecooling water temperature is lower than 35° C. and the program proceedsto step 79 if it is judged yes and to step 81 if no. In step 79 isjudged by the input signal from the vehicle speed sensor 35 whether ornot the vehicle speed is lower than 40 km/h and the program proceeds tostep 80 if it is judged yes and to step 81 if no. In step 80 isprohibited the third speed. Namely, when the cooling water temperatureis lower than 35° C. and the vehicle speed is lower than 40 km/h, thethird speed is prohibited, and when the cooling water temperature ishigher than 35° C. or the vehicle speed is higher than 40 km/h thoughthe vehicle is run only by the first and second speeds, up-shift to thethird speed is performed in a predetermined running range in the samemanner as in the completion of warming-up. In step 81 is judged whetheror not the vehicle speed is lower than 60 km/h and the program proceedsto step 82 if it is judged yes and terminates if no. In step 82 isprohibited the fourth speed. Namely, when the cooling water temperatureis lower than 60° C. and the vehicle speed is lower than 60 km/h, thefourth speed is prohibited. However, when the cooling water temperatureis higher than 60° C. or the vehicle speed is higher than 60 km/h, theup-shift to the fourth speed is performed in a predetermined runningrange in the same manner as in the completion of warming-up.

FIG. 5 is a schematic diagram of an embodiment of the device accordingto the present invention. The vehicle speed sensor 35 is constitutedfrom a magnetized disk 86 rotating integrally with a cable connected tothe output shaft of the automatic transmission 36 and a reed switch 87opened and closed along with the rotation of this magnetized disk 86.The reed switch 87 is connected on one end with a voltage terminal 88 ata predetermined voltage B and on the other end with the input terminalof F/V (Frequency/Voltage) converter 89. The output voltage Vs of F/Vconverter 89 is sent to inversion terminals of comparators 90, 91, andto noninversion terminals of the comparators 90, 91 are connectedrespectively terminals 92, 93 at predetermined voltages V1, V2. Thepredetermined voltages V1, V2 correspond respectively to the vehiclespeeds 60 km/h, 40 km/h for example. FIG. 6 shows the relationshipbetween input frequency Fv, i.e. vehicle speed and the output voltage Vsin F/V converter 89. Vs is a linear function of FV. The watertemperature sensor 30 comprises a thermistor, having voltage B ofterminal 88 applied through a resistance 97. The output voltage Vth ofthe water temperature sensor 30 is connected to the non-inversionterminals of comparators 98, 99, and to the inversion terminals of thecomparators 98, 99 are respectively connected terminals 100, 101 atpredetermined voltages V3, V4. The predetermined voltages V3, V4correspond respectively to the cooling water temperatures 60° C., 35° C.for example. FIG. 7 shows the relationship between the cooling watertemperature and the output voltage Vth of the water temperature sensor30. Vth is inversely proportional to the cooling water temperature.These comparators 90, 91, 98 and 99 produce "1" (hereinafter high levelvoltage is defined as "1" and low level voltage as "0" respectively)only when the input voltages Vs, Vth at the inversion terminals arelower than the input voltages V1, V2, V3, V4 at the noninversionterminals. The output of the comparators 90, 98 are sent to AND circuit104 and the outputs of comparators 91, 99 is sent to AND circuit 105.AND circuit 106 receives the fourth speed signal at one input terminaland the output of AND circuit 104 at the other input terminal through aninverter 107. AND circuit 108 receives the third speed signal at oneinput terminal and the output of the AND circuit 105 at the other inputterminal through an inverter 109. The outputs of the AND circuit 106,108 are sent respectively to a solenoid 45A for the fourth speed and asolenoid 45B for the third speed in the hydraulic control circuit.

Since the outputs of the comparators 90, 98 are both "1" when thevehicle speed is lower than 60 km/h and the cooling water temperature islower than 60° C., the output of the AND circuit 104 is "1" and thus oneinput of the AND circuit 106 sent through the inverter 107 is "0". Thus,the fourth speed signal is not sent to the solenoid 45A for the fourthsignal and the performance of the fourth speed is prohibited. However,the output of the AND circuit 104 is "0" and the input of the ANDcircuit 106 at the inverter 107 side is "1" when the vehicle speed is atleast 60 km/h though the cooling water temperature is lower than 60° C.,so that the fourth speed signal can pass through the AND circuit 106 topermit the performance of the fourth speed.

Since the outputs of the comparators 91, 99 are both "1" when thevehicle speed is lower than 40 km/h and the cooling water temperature islower than 35° C., the output of the AND circuit 105 is "1" and thusinput of the AND circuit 108 at the inverter 109 side is "0" . Thus, thepassage of the third speed signal through the AND circuit 108 is blockedand the performance of the third speed is prohibited. However, since theinput of the AND circuit 108 at the inverter 109 side is 0 when thevehicle speed is at least 40 km/h though the cooling water temperatureis lower than 35° C., the third speed signal can pass through the ANDcircuit 108 to permit the performance of the third speed.

Thus, according to the present invention, when the vehicle is run withhigh vehicle speed though the engine is still in the warming-up and lowtemperature range, the engine can be run on a speed change stage havingsmall reduction gear ratio, i.e. on high speed stage without damagingthe drivability of the engine. Consequently, efficiency of fuelconsumption in the high speed travelling at the low engine temperaturecan be improved and the amount of noxious components purged can berestrained.

What is claimed is:
 1. A speed change method of an automatictransmission for a vehicle, the method comprising the followingsteps:defining shift points in relation to vehicle speed andindependently of engine temperature; carrying out a speed change on thebasis of said shift points; inhibiting the transmission from being in ahigher speed condition under all vehicle operating conditions whenengine temperature is lower than a predetermined temperature and vehiclespeed is lower than a predetermined speed; and allowing the transmissionto be in a higher speed condition when engine temperature is lower thansaid predetermined temperature and vehicle speed is higher than saidpredetermined speed, or when engine temperature is higher than saidpredetermined temperature.
 2. A speed change method as defined in claim1, wherein the temperature of the engine is detected from temperature ofcooling water.
 3. A speed change method as defined in claim 1, whereinthe automatic transmission is of a four forward speed type and when theengine temperature is lower than a first temperature value and thevehicle speed is lower than a first vehicle speed value a fourth speedis prohibited from being performed.
 4. A speed change method as definedin claim 3, wherein when the engine temperature is lower than a secondtemperature value which is lower than the first temperature value andthe vehicle speed is lower than a second vehicle speed value which islower than the first vehicle speed value a third speed is prohibitedfrom being performed.
 5. A speed change method as defined in claim 1,wherein the temperature of the engine is detected from temperature oflubricating oil.
 6. A speed change method as defined in claim 1, whereinthe temperature of the engine is detected from temperature of cylinderhead.